In continuous blood seprators, whole blood is separated into various fractions, e.g., red blood cells, plasma, and platelets. In such apparatus, it is desirable to know if there is spillover on one type of component (e.g., red cells) into an outflow line for a different component (e.g., platelets).
In a platelet collection procedure, the platelets are collected in a bag, and the red blood cells and plasma are returned to the patient. The bags of platelets can be stored, for example, up to five days, before use. Bellhouse U.S. Pat. No. 4,657,383 and Bonner U.S. Pat. No. 4,522,494 disclose analyzing volumes of collected platelets stored in bags for platelet viability by sensing the light passed through samples that are still in the bags and are caused to flow back and forth, one measurement parameter being concentration of platelets in the bags.
Khoja et al. U.S. Pat. No. 4,132,349 discloses monitoring the optical density of light passing through a white blood cell outflow line and using the optical density to control outflow pump motors.